Dilatation catheters are devices that have an inflatable balloon at the distal end and are utilized in medical procedures such as angioplasty to eliminate stenoses or blockages. The balloons are inserted into vessels in the body to open stenoses or blockages in the vascular system, usually by means of a catheter having a balloon at its distal end. To this end, the catheters may be inserted into a blood vessel, advanced through the blood vessel to a target site (i.e. the location of the stenosis or blockage) and the balloon is then inflated by supplying a liquid such as a radiopaque substance for angiography, through an inflation lumen. The inflation of the balloon causes stretching and expansion of the target site, i.e. a blood vessel, in order to eliminate the stenosis or blockage, thereby reestablishing acceptable blood flow. There are various types of catheters having single or multiple lumens, some of which are over-the-wire and some of which are not.
Dilatation balloons are typically made of polymeric materials including nylon, polyether-polyester block copolymers, poly(amide-ether-ester) block copolymers, polyethylene terephthalate, polytetrafluoroethylene, polyvinyl chloride, polyurethanes, polyetherurethanes, polyesterurethanes, polyurethane ureas, polyurethane siloxane block copolymers, polyethylene, polypropylene or other similar extrudable thermoplastic, polymeric materials, or composites thereof. Polymeric films, however, can be damaged by abrasion and can puncture during use, especially when in the presence of calcified lesions. Polymeric balloon catheters can also be compromised during manufacturing. For example, pinholes can be formed during stent crimping.
Some balloon catheters are designed to supply a moderate amount of heat to a target site. Thermal energy is capable of denaturing the tissue and modulating the collagenous molecules in such a way that treated tissue becomes more resilient. Thermal energy can be supplied to a target site using a radiofrequency ablation catheter. Radiofrequency energy, when coupled with a temperature control mechanism, can be supplied precisely to the electrode-to-tissue contact site to obtain the desired temperature for treating a tissue. Radiofrequency ablation catheters, however, require a permeable membrane to conduct electrons from the coil in the center of the balloon through the thickness of the membrane and into the tissue. The holes in the membrane need to be small enough to ensure that the balloon does not burst, but still large enough to conduct. Some designs use layered structures having an inner permeable layer and an outer dielectric coating, leaving windows to act as electrodes.
Other medical devices include medical implants. In some cases, certain medical implants can be made of polymers or other materials having certain desired bulk material properties. Certain implant materials, however, can be prone to an inflammatory response and/or bacterial growth, which can cause clotting or other undesirable clinical outcomes. For example, medical implants can include heart valves, occlusions (e.g., left atrial appendage occlusions), vaginal meshes, stents, and stent grafts.